Question 1

Can CA 19-9 be used to screen for pancreatic cancer in healthy people?

Accepted Answer

Because of the low prevalence of pancreatic cancer in the general population and the possibility of elevated tumor marker levels in conditions other than pancreatic cancer, the CA 19-9 assay is not accurate enough to be used as a screening tool in the asymptomatic population. CA 19-9 serum levels have a sensitivity and specificity of 79-81% and 82-90% respectively for the diagnosis of pancreatic cancer in symptomatic patients, but are not useful as a screening marker because of low positive predictive value. The test is primarily used for monitoring known cancer cases rather than detecting cancer in healthy individuals.

Question 2

What other conditions besides cancer can cause elevated CA 19-9 levels?

Accepted Answer

Non-cancerous conditions that can cause elevated CA 19-9 levels include gallstones that block bile ducts, cholangitis (infection of the bile ducts), pancreatitis (inflammation of the pancreas), cirrhosis of the liver, bile duct disease including blockage or infection, liver disease, and cystic fibrosis. CA 19-9 may also increase in benign pancreatobiliary, hepatic and pulmonary diseases, thyroiditis, diabetes mellitus, and autoimmune diseases. This is why healthcare providers always consider the complete clinical picture when interpreting results.

Question 3

How often should CA 19-9 levels be monitored during cancer treatment?

Accepted Answer

If the CA 19-9 level was raised before treatment, patients may be tested during and after treatment to judge success. Changes in CA 19-9 levels help doctors see if the tumor is growing, staying the same or getting smaller, which helps doctors decide if they should change treatment or run more tests or scans. The frequency of monitoring depends on the individual treatment plan and should be determined by the healthcare team. Some patients may need testing every few weeks during active treatment, while others may be monitored less frequently.

Question 4

Why might some people have normal CA 19-9 levels even with pancreatic cancer?

Accepted Answer

CA 19-9 is related to the Lewis blood group antigens and only patients belonging to specific blood groups will express the CA 19-9 antigen. Lewis antigen-negative phenotypes occur in 5-10% of population which lack the enzyme required for antigen epitope production, limiting the use of CA 19-9 as a universally applicable biomarker. Additionally, CA 19-9 levels are increased in only about 40% of stage I pancreatic cancers, and levels may be normal even up to several months prior to the clinical signs of pancreatic cancer. This is why additional diagnostic methods are always necessary.

Question 5

Can medications or treatments affect CA 19-9 test results?

Accepted Answer

During radiation therapy, CA 19-9 levels might be raised as dying cancer cells release CA 19-9, and for this reason, the test is not usually done while the patient receives radiation treatment. As the mucin is excreted exclusively via the liver, even slight cholestasis can lead to clearly elevated CA 19-9 serum levels, and erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies. It's important to inform your healthcare provider about all medications and treatments you're receiving before testing.

CA 19-9 (Pancreatic Cancer Marker)